Packing materials in the shape of tubular elements, which are sealed longitudinally by means of bonding at least one side and are heat-sealable in the cross-sectional direction for use as bags, are already known. For the most part, the wall of the tubular element, which is produced from a folded sheet or front two overlapping sheets, consists of an outer layer or film which is made of a plastic material that is impermeable to gases and of at least one inner layer or film which is made of a thermoplastic material that is heat-sealable and compatible with the product to be packed.
The two layers or films are intimately connected, and the inner layer or film may have embossing, that is, a network of channels which promote the outlet of air for the formation of a vacuum in the bag at the time of the bag's sealing for use. However, the embossing only allows the evacuation of air for the vacuum-packing.
It is an object, the purpose of the present invention is to provide a packing material having a new, original design, which is obtained with a combination of various layers or films made of plastic material and with which two functions may be obtained at the same time within the scope of the resulting bag, with the impermeability towards the outside and the heat-sealability remaining constant:
the complete discharge of air for the formation of the vacuum;
the control of a nontoxic, inert gas which, when progressively released into the bag, permits the more prolonged preservation of the packed product, without having to resort to common preform compositions.
Another purpose of the present utility model is to provide a bag which consists of at least one inner surface formed by a film with blisters or bubbles which are capable of defining, among themselves, on the surface of the film, a network of channels for the evacuation of air and of containing the gas intended to be released into the bag in order to better preserve the packed product. According to the invention, a tubular element for the formation of bags for the vacuum-packing of products if provided including a first sheet formed of an outer layer of film which is made the material which is impermeable to gas and at least one inner layer of film which is made of a heat-sealable thermoplastic material. A similar second sheet is formed of an outer layer which is impermeable to gas and an inner layer which is made of a heat-sealable thermoplastic material. The first and second sheets are connected at an upper edge and a lower edge to form a tubular article. One of the inner layers is formed with a plurality of bubble structures which, when the first sheet is pressed against the second sheet, delimits a network of surface channels, defined between adjacent bubble structures. The bubble structures contain a non-toxic or inert gas to be progressively released into the bag for preservation of the packed product. In the case of an additional inner layer the additional inner layer is made of the same thermoplastic material as the inner layer of the first sheet and the inner layer of the second sheet.